Seawater Quality Research Articles

Improving green sea urchin (Strongylocentrotus droebachiensis) hatchery production by determining effective settlement cues and post-settlement conditions

Hatchery production methodologies of Northeastern U.S. green sea urchins (Strongylocentrotus droebachiensis) have yielded low settlement success and post-settlement survival (approximately 1–5%) contributing towards high costs for producing juveniles for this emerging aquaculture species. These are likely attributed to hatchery operations needing to optimize settlement cues and post-settlement food supplies. This study examined a range of potential settlement cues using adult conspecifics or a benthic diatom biofilm (Cylindrotheca closterium or Nitzschia sp.) alone, or in combination with seawater conditioned with conspecifics or macroalga (Saccharina latissima or Ulva lactuca). This study also examined whether sea urchin post-settlement survival and growth would improve using a benthic diatom food source (C. closterium or Nitzschia sp.) alone or in combination with an additional macroalga food source (S. latissima or U. lactuca). Both trials were conducted under hatchery ambient (control 12 °C) or elevated (14 °C) temperatures to determine whether temperature elevation could enhance S. droebachiensis settlement success and post-settlement growth. This study also examined what influence biofilm age (1, 4 and 8 weeks) and seawater salinity (26, 30, 33 and 36) had on settlement success to help towards optimizing hatchery methods. This study did not improve post-settlement survival causing it to remain a significant barrier in mass producing juveniles, but it did increase juvenile growth by 30–40% and reduce growth variability when fed the benthic diatom C. closterium in combination with U. lactuca. This combination also served as an adequate settlement cue for this species. The use of a conspecific influenced biofilm substantially improved settlement success from 1 to 5% to 50–80%. Seasonal timing and age (4 weeks) of this biofilm indicated importance in yielding this success which will be location specific. The use of conspecific biofilms for improving post-settlement survival requires further investigation and is worth examining in combination with C. closterium and U. lactuca towards enhancing S. droebachiensis production in the Northeastern U.S. Elevating seawater temperature by 2 °C had no significant effect on settlement, growth, or survival in this study. Salinities of 30–33 were optimal yielding 3–7 times more settlement compared to salinities 27 and 36. This study highlights that settlement trials need to incorporate post-settlement survival measurements for at least 1–2 months to truly reflect the effectiveness of method interventions and consider extending the time before turning seawater flow back on into settlement tanks from 24 to 48 h by up to 72–96 h to facilitate greater settlement success if seawater quality parameters permit it.

Changes in mariculture and offshore seawater quality in China during the past 20 years

Mariculture can provide a large amount of food without occupying land resources, which provides important assistance for humans to achieve sustainable development. In this paper, China, where the output of mariculture exceeds half of the global output, is taken as the research area. Based on the spatial distribution data of three periods of mariculture along the coast of the Chinese Mainland in 2000, 2010, and 2020 obtained from remote sensing images and from the perspective of the mariculture center, the spatial development of mariculture in three periods in China is explored. Furthermore, by spatially overlaying mariculture data with concurrent water quality data, the relationship between the development and changes in the mariculture center and the seawater quality in different geographical environments was analyzed at the national scale.. We found that (1) Mariculture in China exhibits a noticeable geographical differentiation, with the scale and development speed of mariculture in northern regions surpassing that of the southern regions. (2) Good seawater quality is the prerequisite for the formation of mariculture centers, while water quality deterioration is detrimental to the development of mariculture. (3) The formation of large-scale high-density mariculture centers does not necessarily lead to deterioration of the seawater quality. Furthermore, we found that the water depth is an important factor leading to the spatial distribution pattern of mariculture in China, i.e., dense in the north and sparse in the south. The flow velocity is an important factor determining the water quality changes in mariculture centers.

Deriving seawater quality criteria of tris(2-chloroethyl) phosphate for ecological risk assessment in China seas through species sensitivity distributions

Tris(2-chloroethyl) phosphate (TCEP), one of the widely used organophosphorus flame retardants (OPFRs), has been frequently detected in the marine environment in the seas off China. The existing freshwater biotoxicity data are not suited to derivation of the seawater quality criteria of TCEP and evaluating the associated ecological risks. This study aimed at deriving water quality criteria (WQC) of TCEP for marine organisms based on species sensitivity distribution (SSD) approach using the acute toxicity data generated from multispecies bioassays and chronic toxicity data by converting acute data with the acute-to-chronic ratios (ACRs); the derived WQC were then used to evaluate the ecological risk for TCEP in China Seas. According to median effective concentration (EC50) and median lethal concentration (LC50), TCEP had a moderate or low toxicity to eight marine species selected, among which mysid Neomysis awatschensis (96h-LC50 of 39.65 mg/L) and green alga Platymonas subcordiformis (96-h EC50 of 395.42 mg/L) were the most sensitive and the most tolerant, respectively. The acute and chronic hazardous concentrations of TCEP for 5% of marine species (HC5) were estimated to be 29.55 and 2.68 mg/L, respectively. The short-term and long-term WQC were derived to be 9.85 and 0.89 mg/L, respectively. The risk quotient (RQ) values indicated that TECP at current levels poses a negligible risk to marine ecosystems in China. These results will provide valuable reference for the government to establish a seawater quality standard for TCEP.

Spatial distribution and pollution assessment of heavy metals in surface and bottom water along the eastern part of the Egyptian Mediterranean coast

Seawater contamination with heavy metals (HMs) as a result of anthropogenic activities is a global challenge due to its negative impacts on marine environments and coastal communities. This study investigates the distribution of HMs (Fe, Zn, Cu, Mn, Cd, Ni and Co) and assesses the quality of surface and bottom seawater. Samples were collected in winter 2020 and summer 2021 from eleven sectors along the eastern Egyptian Mediterranean Sea coast. The water quality was evaluated using Water Quality Index (WQI), Metal Index (MI), heavy metal pollution index (HMI) and Metal Pollution index (MPI). The results indicated that, Eastern Harbour, Abu-Qir and Port Said sectors were polluted with HMs. Based on Two-Way ANOVA test there was seasonal variation for dissolved HMs (Zn, Ni, Cd and Mn in bottom layer and Cu in surface layer), while, (Cd, Co, Cu, Zn and Mn (in bottom layer)) revealed spatial differences among sectors.

Underwater quantum key distribution with continuous-variable via photon additions

Quantum key distribution with continuous-variable (CVQKD) provides an alternative way for the security improvement of underwater optical communication, but facing into the awkward situation of short distance. For this reason, here we exploit photon addition operation at the emitter into enhancing the performance of underwater CVQKD. Based on numerical simulation, it is shown that applying photon-addition non-Gaussian operation between entangled resource and the sender can further enhance both the secure key rate and the transmission distance, compared to apply photon subtraction operation between entangled resource and the receiver. In addition, the influence of seawater quality factors in underwater CVQKD system is also considered, so as to provide technical support for underwater safety communication.

The Perceptions and Risk Reduction Strategies of Small-Scale Salt Farmers on Madura Island

Salt farming is considered a risky venture due to the influence of both internal and external factors. Therefore, this study aimed to describe farmers' perceptions regarding the causes, opportunities, and impacts of risks to develop a risk reduction strategy for salt farming in Madura Island. The study used a multistage sampling method to obtain 120 respondents and was conducted in three regencies: Sampang, Pamekasan, and Sumenep. The first objective was analyzed using the descriptive method, while the second was designed using the Kountur method. Farmers' perceptions showed that seawater quality, wind and temperature, rainfall, soil porosity, price volatility, marketing channels, government policies, capital constraints, and human resource quality could cause risks in salt farming. Several risks were perceived to significantly impact salt farming, such as government policies, partnerships, marketing channels, prices, and capital availability. Therefore, some recommendations to improve the risk reduction strategies included the use of horizontal axis windmills, revitalization of groups and partnerships, and capital strengthening through the effectiveness of the PUGAR (Empowerment of Smallholder Salt Businesses) policy by the development of standard procedures for the timely and targeted distribution of the aides.
 
 Keywords: perception, risk, salt, strategy

The impact of destruction of the Kakhovka dam on the environmental status of the Odesa area of the Black Sea

The paper provides a chronological description of the aftermath and the effect of blowing up the Kakhovka hydroelectric power plant dam by Russian occupation forces of 6 June 2023 on the seawater quality in the coastal zone of Odesa agglomeration, according to the results of operational environmental monitoring in the early weeks upon the man-made disaster. Such a description is indispensable for assessing the scope of pollution of marine water areas and calculation of the damage inflicted on the marine ecosystem and its natural resources, adjustment and verification of mathematical models which will further be used to prognosticate the consequences of the dam destruction for the marine ecosystem. According to the data published in open sources, development of the environmental, sanitary and microbiological situation in the coastal zone of the city of Odesa over June 2023 is described, the dynamics of some indices of the sea water quality are shown, and the pollutants the concentration of which exceeded the maximum permissible concentrations set for them, as well as sanitary and microbiological indices, according to which the population is forbidden from swimming in the sea, are indicated. In addition, as a consequence of the abnormal desalination of sea waters and the inflow of a large amount of nutrients and organic matter into the sea, the phenomenon of algal bloom is described, and a qualitative forecast of its consequences is provided. It is concluded that owing to the accumulated reserves of organic matter in the bottom sediment probability of hypoxic conditions and suffocation of hydrobionts in the summer periods will increase in the years to follow. It is in view of the accumulation of pollutants in bottom sediments and the expected secondary pollution of sea water that the biological diversity of the marine ecosystem within the Odesa region will degrade and the quality of its biological resources will deteriorate.

Hydrography of Northern Thermaikos Gulf based on an integrated observational-modeling approach

The Northern Thermaikos Gulf is a semi-enclosed coastal region of the Aegean Sea, characterized by anthropogenic and natural stresses such as intense industrial and agricultural activities, urban outflows, and several river discharges facing severe pollution events. The main motivation of this study is to investigate the prevailing oceanographic conditions of Northern Thermaikos Gulf, which are associated with the quality of the semi-enclosed basin's water masses. The hydrography and the hydrodynamic circulation patterns are revisited, based on the findings of a multi-platform observational study, conducted during a recent annual cycle, from June 2021 until May 2022. The observational findings are supported by a three-dimensional high-resolution hydrodynamic model (Deltf3D-Thermaikos) with updated freshwater input from all important land sources. The physical connectivity between the sub-basins of Thermaikos, the renewal of its northern coastal areas and the seawater quality are strongly related to the variability of wind-induced circulation. Northerly and southerly winds affect the spreading of the nutrient-rich riverine waters, discharged at the west coast of the gulf. The prevailing northerly winds contribute to the southward removal of the polluted sea surface and riverine waters, enhancing the cyclonic circulation around the gulf, allowing the inflow of clearer Aegean Sea Waters along the eastern coasts of the gulf. Northerlies also promote a connectivity pathway between the environmentally stressed Thessaloniki Bay (urban seafront) and the commonly less polluted southeastern coasts of the central basin. Southerlies mainly confine riverine waters in the western and northern coastal regions, weaken the renewal ability of the enclosed basins, and impose the formation of anticyclonic, mesoscale, circulation eddies in the outer and central areas.

Effect of hatchery and mariculture activity at the northwest coastal area of Bali on water quality and plankton community

The northwest coastal area of Bali is currently for the development of marine fish hatcheries and cage farming. This study aims to influence the hatchery and aquaculture activities of marine fish cages in the northwest coastal area of Bali on seawater quality and plankton community. The parameters observed on water quality were total suspended solids, temperature, transparency, pH, dissolved oxygen, Salinity, ammonia, nitrite, nitrate, phosphate, C-organic, total organic matter, and plankton community on diversity, similarity, and dominancy index. The results of water quality observations found that water temperature was 27.5-29.1°C, TSS 0.028-0.046 ppm, transparency 7.4-12.8 m, pH 8.1-8.3, DO 5.4-6.9, Salinity 33.2-34.1, ammonia, 0.01-0.04 ppm, nitrite 0.028-0.041 ppm, nitrate 0.018-0.036 ppm phosphate 0.026-0.038 ppm, C-Organic 0.65-0.74 ppm, TOM 0.75-1.23 ppm. Found 38 genera and 10 phyla of plankton, with an abundance was 258-26,546 ind/L, an index of the diversity of 0.89-2.15, an index of similarity of 0.22-0.64, and an index of dominancy 0.18-0.43. From these results, it can be concluded that the coastal waters of northwest Bali are in the criteria that have not been polluted and are good for marine fish farming. The northwest coastal area of Bali must be managed properly so that marine fish farming can be sustainable.

Vertical and horizontal distribution model of lead (Pb) in Padelegan Waters, Pademawu District, Pamekasan Regency

Seawater quality is importantly used in salt production, but it could be contaminated due to input of anthropogenic wastewater. This study aims to understand the quality of the water and the content of Pb in seawater, which will be used as raw material for salt production. Descriptive research methods and purposive sampling methods were used for the research method and the determination of the sampling respectively. Sampling of seawater was carried out water sampler, followed by analysis of heavy metal Pb based on APHA 1998 using Atomic Absorption Spectrophotometry (AAS). The concentration of Pb on the surface ranged from 0.6332 to 1.0815 mg/L, in the water column from 0.5842 to 1.0516 mg/L, and in the bottom waters from 0.5571 to 0.9375 mg/L, according to the findings. The horizontal distribution of the Pb showed an increasing trend towards the sea with concentrations ranging from 0.6332 to 1.0815 mg/L. Meanwhile, the concentrations of Pb in surface waters increased vertically, ranging from 0.5571 to 1.0815 mg/L. The horizontal distribution is higher towards open sea, while vertical distribution is higher towards the water surface. Seawater in vicinity of study area is still probably used although caution must be observed regarding to the Pb content.

Pollution Index Analysis of Seawater in Nickel Smelter Bantaeng’s Port

Good water quality conditions are significant for supporting the life of organisms and providing security for community activities. Water quality status determination is needed to monitor water quality pollution. Seawater quality is a critical aspect of environmental science and ecological research due to its profound impact on marine ecosystems, human health, and various community activities. It has been a significant concern because of its direct influence on marine ecosystems, human activities, and public health. This study aims to determine the pollution index referred to as physical-chemical-dissolved metal parameters in the nickel smelter port in Bantaeng Regency. A sampling of water quality was carried out at three sampling points. Then the results were compared with seawater quality standards for marine biota referred to the Keputusan Menteri Lingkungan Hidup No. 51/2004 on Seawater Quality Standards. Observation and analysis of water conditions are conducted in situ and ex-situ, with testing carried out at Ak-Manufaktur Laboratory and BBIHP Laboratory. The results of the pollution index calculation show that the waters around the nickel smelter port are in the moderately polluted category. The pollution index values were obtained in the moderately dirty variety at points 1: 8.515, 2: 9.652, and 3: 9.792. Environmental parameters still following quality standards for marine biota include temperature, pH, salinity, DO, and nickel (Ni).Keywords: pollution index; physical; chemical; metals; smelter

Heavy metals contaminant of shrimp paste products and risk assessment in Thailand

Shrimp paste (ka-pi) is one of the fermented fishery products that has been widely consumed in Thailand, but the risk assessment of different material sources of shrimp paste is limited. This study aims to investigate the heavy metal concentration of arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) in shrimp paste products in Thailand. Thirty shrimp paste product samples were collected from the local markets and were segregated based on the areas where raw materials were collected from. These areas include the Andaman Sea and the Gulf of Thailand. The modified method was validated by checking the linearity between instrument signal response and pure reference standard of a single element using r2 value of external standard and five concentration levels with > 0.9995. The recoveries were within 97% and 103% for all the studied metals. The Limit of Detection (LOD) ranged between 0.005 – 0.25 (mg/kg), and the Limit of Quantification (LOQ) was between 0.016 – 0.598 (mg/kg). As and Hg contaminants were found in all 30 sample products. The health-risk estimation indicated that the hazard quotient for As was the highest, and 8 out of 30 samples from both sampling areas were found to have unacceptable levels. This study presents results that the carcinogenic risk of all 30 samples from the Andaman Sea and the Gulf of Thailand had As levels higher than the acceptable limit. The findings of this study can serve as a useful baseline for taking protective measures and to reduce heavy metal contamination of shrimp paste products in Thailand. The results also suggest measures to improve the seawater quality to protect marine animals from seawater pollution.

Seawater quality criteria and ecotoxicity risk assessment of zinc oxide nanoparticles based on data of resident marine organisms in China

Water quality criteria (WQC) for zinc oxide nanoparticles (ZnO NPs) are crucial due to their extensive industrial use and potential threats to marine organisms. This study conducted toxicity tests using marine organisms in China, revealing LC50 or EC50 values for ZnO NPs ranging from 0.36 to 95.6 mg/L across seven species, among which the salinity lake crustacean zooplankton Artemia salina exhibited the highest resistance, while diatom Phaeodactylum tricornutum the most sensitive. Additionally, the EC10 or maximum acceptable toxicant concentration (MATC) values for ZnO NPs were determined for five species, ranging from 0.03 to 2.82 mg/L; medaka Oryzias melastigma demonstrated the highest tolerance, while mysis shrimp Neomysis awatschensis the most sensitive. Based on the species sensitivity distribution (SSD) method, the derived short-term and long-term WQC for ZnO NPs were 138 μg/L and 8.37 μg/L, respectively. These values were further validated using the sensitive species green algae Chlorella vulgaris, confirming effective protection. There is no environmental risk observed in Jiaozhou Bay, Yellow River Estuary and Laizhou Bay in the northern coastal seas of China. This study provides important reference data for the establishment of water quality standards for nanoparticles.

Collapse of scallop Nodipecten nodosus production in the tropical Southeast Brazil as a possible consequence of global warming and water pollution

Mollusc rearing is a relevant global socioeconomic activity. However, this activity has faced severe problems in the last years in southeast Brazil. The mariculture scallop production dropped from 51,2 tons in 2016 to 10,2 tons in 2022 in the Baia da Ilha Grande (BIG; Rio de Janeiro). However, the possible causes of this collapse are unknown. This study aimed to analyze decadal trends of water quality in Nodipecten nodosus spat and adult production in BIG. We also performed physical-chemical and biological water quality analyses of three scallop farms and two nearby locations at BIG in 2022 to evaluate possible environmental stressors and risks. Scallop spat production dropped drastically in the last five years (2018–2022: mean ± stdev: 0.47 ± 0.45 million). Spat production was higher in colder waters and during peaks of Chlorophyll a in the last 13 years. Reduction of Chlorophyll a coincided with decreasing spat production in the last five years. Warmer periods (>27 °C) of the year may hamper scallop development. Counts of potentially pathogenic bacteria (Vibrios) and Escherichia coli were significantly higher in warmer periods which may further reduce scallop productivity. Shotgun metagenomics of seawater samples from the five studied corroborated these culture-based counts. Vibrios and fecal indicator bacteria metagenomic sequences were abundant across the entire study area throughout 2022. The results of this study suggest the collapse of scallop mariculture is the result of a synergistic negative effect of global warming and poor seawater quality.

ANALISIS KUALITAS PERAIRAN BUDIDAYA RUMPUT LAUT DI DUSUN SALIONG DESA BATU BOY SEBAGAI DAMPAK GAGAL PANEN

Background: The production of seaweed cultivation in Saliong Hamlet, Batu Boy Village, hasdecreased, and there have even been crop failures in the last five years. For this reason, an analysisof the factors suspected of influencing the failure is needed. The purpose of this study was to analyzethe quality of seaweed cultivation waters in Saliong Hamlet, Batu Boy Village by using physicalchemical factors of the waters.Methods: There are three stations used for sampling. The physical and chemical parameters of thewaters measured include temperature, brightness, current speed, water depth, pH, salinity, TDS,DO, BOD, phosphate, heavy metal mercury (Hg) and cyanide. To determine water quality, the resultsof measuring physical-chemical water parameters will be compared with sea water quality standardsfor marine biota and quality standards for seaweed cultivation based on experts in the field.Results: The research results showed that temperature, depth, TDS, phosphate and heavy metalmercury did not meet quality standards. While the parameters of brightness, turbidity, currentvelocity, pH, salinity, DO, BOD and cyanide are still in accordance with the quality standards forseaweed cultivation.Conclusion: The quality of the waters in the seaweed cultivation area in Saliong Hamlet still meetsthe quality standards and some does not comply with the quality standards. The occurrence ofseaweed harvest failure can be caused by the presence of physical-chemical factors in the watersthat are less supportive.

Ecological risk assessment of selected contaminants in seawater, sediment and some fish species from Alexandria beaches, South-Eastern Mediterranean Sea, Egypt

The present study aims to investigate the hydrographical characteristics, nutrient salts, and heavy metals (HM) to estimate the contamination status of selected coastal beaches along the Alexandria coastal area in the southeast Mediterranean Sea. Water and sediment samples were collected from 8 beaches along the cost of Alexandria, while 122 fish samples representing 10 species were collected from 2 beaches representing two ports at Alexandria city. All samples were subjected to specific analyses to assessment of ecological risks at study area. The study indicated that the seawater quality of the investigated beaches varied between medium to good based on the Water Quality Index (WQI = 0.233–0.713). Moreover, the highest average concentration in water was observed for Fe (33.624 μgl−1) and the lowest was detected for Cd (0.050 μgl−1). HM in sediment have the same trend of these HM in water. The most of beaches’ sediments were classified as non-contaminated (PI < 1) with all examined HM. Hazard Quotient and Hazard Index (HQ &HI < 1) this indicated that the lack of non-carcinogenic impacts for children and adults due to dermal contact with sediments of all beaches. The most abundance HM in fish were Fe and Zn. Bioaccumulation factors (BAF) in fish muscles was evaluated. MPI (Metal Pollution Index) of HM in the investigated species ranged from (0.381–2.216) in Pomatomus saltatrix and Scomberomorus commerson species respectively. HQ, HI, EDI (Estimated Daily Intake), and TR (Target Risk) values showed that the examined species are still safe for human consumption.

Spatiotemporal Nutrient Patterns, Stoichiometry, and Eutrophication Assessment in the Tieshan Bay Coastal Water, China

Land-source inputs into coastal water have increased remarkably in recent years, resulting in the deterioration of water quality, eutrophication, and algae blooms. However, we have limited understanding of spatiotemporal nutrient patterns, stoichiometry, and eutrophication assessment in Tieshan Bay coastal water at present. To investigate the rapid development of the coastal areas in Tieshan Bay in the South China Sea, nutrients and other physicochemical parameters were observed in Tieshan Bay during the normal season (April), wet season (July), and dry season (October) in 2021. The results showed that the average concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and chemical oxygen demand (COD) in Tieshan Bay are 0.071 ± 0.115 mg/L, 0.008 ± 0.013 mg/L, and 0.71 ± 0.219 mg/L, respectively. DIN/DIP ratio ranges from 9.1–69.3, with an average value of 19.9 ± 19.2, which exceeds the Redfield value, behaving P limitations. In addition, the mean eutrophication index (EI) was low in Tieshan Bay, with an average value of 0.5 ± 1.5. Moreover, the hotspot coastal water with high DIN, DIP, and COD concentrations was located in the upper half of Tieshan Bay in all seasons. In addition to the DIN, DIP, and COD contributions to EI, the average contribution rates of DIN, DIP, and COD are 26.6%, 8.8%, and 64.6%, respectively, which leads to the largest contribution of COD to EI. Furthermore, the average comprehensive index (CI) of organic pollution in Tieshan Bay surface seawater ranged from −1 to 5.6. The seawater near Hepu in S8 station has organic pollution in wet and dry seasons, and Tieshan Bay’s middle region also has slight organic pollution. Additionally, the DIN, DIP, and COD had significant relationships with salinity (p &lt; 0.05), suggesting that coastal water quality is affected by land-based sources input. To achieve the seawater quality target and mitigate regional eutrophication, it is critical to implement land-based source management across the river-bay-coastal water continuum.

Multi-model chain for climate change scenario analysis to support coastal erosion and water quality risk management for the Metropolitan city of Venice

Under the influence of anthropogenic climate change, hazardous climate and weather events are increasing in frequency and severity, with wide-ranging impacts across ecosystems and landscapes, especially fragile and dynamic coastal zones. The presented multi-model chain approach combines ocean hydrodynamics, wave fields, and shoreline extraction models to build a Bayesian Network-based coastal risk assessment model for the future analysis of shoreline evolution and seawater quality (i.e., suspended particulate matter, diffuse attenuation of light). In particular, the model was designed around a baseline scenario exploiting historical shoreline and oceanographic data within the 2015–2017 timeframe. Shoreline erosion and water quality changes along the coastal area of the Metropolitan city of Venice were evaluated for 2021–2050, under the RCP8.5 future scenario. The results showed a destabilizing trend in both shoreline evolution and seawater quality under the selected climate change scenario. Specifically, after a stable period (2021–2030), the shoreline will be affected by periods of erosion (2031–2040) and then accretion (2041–2050), with a simultaneous decrease in seawater quality in terms of higher turbidity. The decadal analysis and sensitivity evaluation of the input variables demonstrates a strong influence of oceanographic variables on the assessed endpoints, highlighting how the factors are strongly connected.The integration of regional and global climate models with Machine Learning and satellite imagery within the proposed multi-model chain represents an innovative update on state-of-the-art techniques. The validated outputs represent a good promise for better understanding the varying impacts due to future climate change conditions (e.g., wind, wave, tide, and sea-level). Moreover, the flexibility of the approach allows for the quick integration of climate and multi-risk data as it becomes available, and would represent a useful tool for forward-looking coastal risk management for decision-makers.

Seasonal nutrients variation, eutrophication pattern, and Chlorophyll a response adjacent to Guangdong coastal water, China

Nutrients were the key biogenic elements for the primary production in coastal water, and the increase of nutrient concentration led to eutrophication and frequent occurrence of harmful algal blooms. However, the seasonal nutrients variation, eutrophication pattern, and Chlorophyll a (Chl-a) response adjacent to Guangdong coastal water were still scarcely. In this study, to clarity the seasonal nutrients variation, eutrophication pattern, and Chl-a, response adjacent to coastal water, the spatiotemporal dissolved inorganic nitrogen (DIN) and phosphorus (DIP) patterns and Chl-a were explored by field observation using 52 stations in the coastal waters of Guangdong Province during the dry (April and May), wet (July and August) and normal (October and November) seasons in 2020. The results showed that the variability of Chl-a, DIN and DIP were significantly different in seasons (P&amp;lt;0.01), and the mean concentrations of Chl-a, DIN and DIP were 11.97 ± 28.12 μg/L, 25.84 ± 35.72 μmol/L and 0.59 ± 0.71 μmol/L.Among them, the mean value of Chl-a increased significantly from 9.99 ± 9.84 μg/L in the dry season to 18.28 ± 38.07 μg/L in the wet season, and then decreased significantly to 7.65 ± 27.64 μg/L in the normal season.The mean DIN value decreased significantly from 30.68 ± 43.58 μmol/L in the dry season to 21.91 ± 35.45 μmol/L in the wet season, and then increased to 24.91 ± 26.12 μmol/L in the normal season. the mean DIP value decreased from 0.58 ± 0.73 μmol/L in the dry season to 0.48 ± 0.65 μmol/L in the wet season and then increased significantly to 0.70 ± 0.73μmol/L in the normal season. In addition, the DIN and DIP concentrations at most monitoring stations met the Grade II national seawater quality standards, and only a few monitoring stations fail to meet the Grade IV national seawater quality standard. The DIN/DIP ratios ranged from 2.05 to 259.47, with an average of 43.77 ± 41.01, far exceeding the Redfield ratio, indicating the presence of P limitation in the nearshore waters of Guangdong Province. Besides, the EI values in the coastal waters of Guangdong Province are higher at 0.00 and 82.51, with an average of 4.16 ± 10.90. DIN and DIP were significantly and positively correlated with COD in each season (P&amp;lt;0.05). Moreover, DIN/DIP showed significantly positive correlations with Chl-a in all seasons (P&amp;lt;0.01), indicating that high Chl-a concentrations could be sustained by the nutrients supply in marine ecosystems. Therefore, it is necessary to strengthen the integrated management of land and sea and effectively mitigate regional estuarine and coastal water eutrophication and harmful algal blooms.

Individual and combined effects of herbicide prometryn and nitrate enrichment at environmentally relevant concentrations on photosynthesis, oxidative stress, and endosymbiont community diversity of coral Acropora hyacinthus

Nitrogen pollution and pesticides such as photosystem II (PSII) inhibitor herbicides have several detrimental impacts on coral reefs, including breakdown of the symbiosis between host corals and photosynthetic symbionts. Although nitrogen and PSII herbicide pollution separately cause coral bleaching, the combined effects of these stressors at environmentally relevant concentrations on corals have not been assessed. Here, we report the combined effects of nitrate enrichment and PSII herbicide (prometryn) exposure on photosynthesis, oxidative status and endosymbiont community diversity of the reef-building coral Acropora hyacinthus. Coral fragments were exposed in a mesocosm system to nitrate enrichment (9 μmol/L) and two prometryn concentrations (1 and 5 μg/L). The results showed that sustained prometryn exposure in combination with nitrate enrichment stress had significant detrimental impacts on photosynthetic apparatus [the maximum quantum efficiency of photosystem II (Fv/Fm), nonphotochemical quenching (NPQ) and oxidative status in the short term. Nevertheless, the adaptive mechanism of corals allowed the normal physiological state to be recovered following 1 μg/L prometryn and 9 μmol/L nitrate enrichment individual exposure. Moreover, exposure for 9 days was insufficient to trigger a shift in Symbiodiniaceae community. Most importantly, the negative impact of exposure to the combined environmental concentrations of 1 μg/L prometryn and 9 μmol/L nitrate enrichment was found to be significantly greater on the Fv/Fm, quantum yield of non-regulated energy dissipation [Y(NO)], NPQ, and oxidative status of corals compared to the impact of individual stressors. Our results show that interactions between prometryn stress and nitrate enrichment have a synergistic impact on the photosynthetic and oxidative stress responses of corals. This study provides valuable insights into combined effects of nitrate enrichment and PSII herbicides pollution for coral's physiology. Environmental concentrations of PSII herbicides may be more harmful to photosystems and antioxidant systems of corals under nitrate enrichment stress. Thus, future research and management of seawater quality stressors should consider combined impacts on corals rather than just the impacts of individual stressors alone.